Air Pollutant Sources, Exposures, & Health Impacts

Detroit is notable for its numerous and large industrial pollution sources, called point sources. These include coal-fired power plants, coke, steel and cement facilities, petroleum refineries, and incinerators, among others. In addition, mobile sources, which include cars, trucks, trains and other vehicles, emit a substantial amount of PM2.5, NOx, and other pollutants.

In addition to the type and quantity of pollutants emitted, exposure is affected by the proximity of emission sources to homes, schools, playgrounds and other frequented locations. The number of people living or going to school or work in an area determines how many people are exposed (1). Detroit has many large neighborhoods and schools adjacent to large industrial facilities. Moreover, about 69,000 Detroit residents live within 150 meters of a major freeway, and 58 Detroit public schools (operating in 2014-15) with an estimated 24,490 students are within 200 meters of a major roadway, distances where concentrations from mobile sources tend to be most elevated (2).

Exposure is also affected by meteorology and source factors, like (smoke) stack height, that influence the dispersion of pollutants. Emissions from many sources, especially those with elevated stacks and those that react in the atmosphere to form new secondary pollutants, like O3, can affect a broad region, and sometimes the areas most affected are several or many miles distant from emission sources. In contrast, highways and industrial sources with low stack heights mostly expose the local neighborhoods. Section 5 of the Resource Manual provides maps of emission sources, the spatial patterns of pollutants resulting from major sources (accounting for meteorology and source characteristics), and estimates of health impacts from PM2.5, O3, and NOx exposures.

Exposures to PM2.5, O3, NO2, and SO2 can have a substantial impact on the health of people living in the Detroit area, as summarized in Table XX. In the Detroit area, outdoor air pollution from all sources is responsible for an estimated 721 premature deaths (571 due to PM2.5, and 150 due to ozone), 1,500 hospitalizations for respiratory and cardiovascular disease, over 200,000 days with respiratory symptoms among children with asthma, 500,000 days of missed work, and more than 990,000 days of missed school (3). The total health burden from PM2.5, O3, NO2 and SO2 totals over 13,500 disability-adjusted live years (DALYs), which is a measure that summarizes health impacts by the time is lost to premature death or poor health. In total, the annual monetized value of the health burden from air pollution is $7.3 billion. These impacts are caused by air pollution from both local and regional sources. Local point sources emissions of PM2.5, NOx, and SO2 cause, each year, an estimated 140 hospitalizations for respiratory and cardiovascular diseases, up to 12,000 respiratory symptom days among children with asthma, 3300 lost days at work, and 29 deaths. Mobile sources cause an estimated 150 hospitalizations, up to 18,000 respiratory symptom days among children with asthma, 1,200 lost days at work, and 11 deaths. Combined, point and mobile sources are responsible for almost 1,200 disability-adjusted live years (DALYs), which summarize health impacts in terms of how much time is lost due to premature death or poor health. In total, the monetized value of the health burden from point and mobile sources is $660 million each year (4). These results are discussed in more detail in Section 5 of the Resource Manual.

3. This analysis used a “no-threshold” assumption when estimating health impacts, that is, there was no level of exposure below which health impacts did not occur. Exposures to PM2.5­, NO2, and O3 are based on area monitoring data. Exposures to SO2 are based on estimates from FRESH-EST, which uses point source emissions. Martenies, SE, Batterman, SA, et al. Health and inequality assessment of the burden of disease attributable to ambient air pollution in Detroit, Michigan. Manuscript in preparation.

4. This analysis used a “no-threshold” assumption when estimating health impacts, that is, there was no level of exposure below which health impacts did not occur. Martenies, SE, Batterman, SA, et al. Health and inequality assessment of the burden of disease attributable to ambient air pollution in Detroit, Michigan. Manuscript in preparation.